Polymers derived from the ring opening polymerization of benzoxazine compounds compete with phenolic, epoxy, and other thermoset or thermoplastic resins in various applications. Benzoxazines can be used as a precursor for chars used in applications where high thermal stability is required such as aircraft disc brakes and thermal insulators.
Benzoxazines have advantages over conventional thermoset resins as the benzoxazine can be readily molded from the melt and then polymerized without releasing substantial amounts of polymerization reaction by-products.
The mechanism of thermally induced ring opening polymerization of benzoxazines is not sufficiently understood to provide control over the molecular weight distribution and branching of the polymer. It is anticipated that the performance of benzoxazine polymers in terms of modulus, processability, and char yield on heating could be improved by controlling the microstructure (branching and molecular weight). Current thermally induced polymerization processes offer little or no opportunity to better understand or control the factors that determine branching, polymer molecular weight, etc. Attempts to use initiators and/or catalysts to polymerize benzoxazine monomers in the past have only slightly modified (shifted) the exotherm temperature of the polymerization.